1. Field
The present disclosure relates to a control apparatus for an internal combustion engine.
2. Description of the Related Art
To date, a feature described in Japanese Patent No. 4952847 is well known as a control apparatus for an internal combustion engine. This internal combustion engine is provided with a turbocharger that has a turbine provided in an exhaust passage, a wastegate valve that opens and closes a bypass passage for bypassing the turbine, an exhaust gas purification catalyst that purifies exhaust gas flowing in the exhaust passage, and a wide-area air-fuel ratio sensor and an O2 sensor respectively provided upstream and downstream of the exhaust gas purification catalyst.
As controls for determining whether or not the exhaust gas purification catalyst is deteriorated, the control apparatus performs a full-close control process for keeping the wastegate valve in a full-closed state, and an air-fuel ratio control process for determining deterioration. In the air-fuel ratio control process for determining deterioration, the air-fuel ratio (hereinafter called “the pre-catalyst air-fuel ratio”) of exhaust gas supplied to the exhaust gas purification catalyst is controlled so as to repeat inversion of the ratio between a predetermined lean value and a predetermined rich value.
While performing the full-close control process and air-fuel ratio control process for determining deterioration, the control apparatus calculates oxygen storage capacity OSC of the exhaust gas purification catalyst and determines deterioration of the exhaust gas purification catalyst on the basis of the calculation result of the oxygen storage capacity OSC. The oxygen storage capacity OSC is calculated by integrating the amount of oxygen release per unit time. In this case, the full-close control process is performed in order to avoid a situation where the wide-area air-fuel ratio sensor cannot accurately detect timing of change in the pre-catalyst air-fuel ratio while the wastegate valve is being opened, and as a result the accuracy of the oxygen storage capacity OSC calculation is reduced.